Molded abrasive article of iron-silicon alloy,and diamond powder

ABSTRACT

AN ABRASIVE ARTICLE CONSISTING OF ABRASIVE PARTICLES DISTRIBUTED IN A METALLIC BASE MATERIAL CONSISTING OF AN ALLOY OF IRON AND SILICON. ALSO INCLUDED IN THE INVENTION IS A NOVEL METHOD FOR PRODUCING THE ARTICLE OF THE INVENTION IN A MOLDING PROCESS UTILIZING, IN COMBINATION, CONTROLLED HEAT AND PRESSURE.

MOLDED ABRASIVE "U.s."c1. 51-309 United States Patent ARTICLE OF IRON-SILICON ALLOY, AND DIAMOND POWDER Michael V. Metzger, Highland Park, and Reginald Pearce,

Bloomingdale, lll., assignors to Engis Corporation, Morton Grove, Ill. 1 No Drawing. Filed Apr. 10, 1972, Ser. No. 242,764 Int. Cl. 324d 3/06; C04b 31/16 13 Claims ABSTRACT on THE DISCLOSURE An abrasive article consisting of abrasive particles distributed in a metallic base material consisting of an alloy ,of iron and silicon. Also included in the invention is a This invention relates to an improved, novel and unique abrasive composition and to the method of converting the composition into an abrasive article having improved physical properties and functional characteristics. More particularly, the invention is directed to an abrasive article in which abrasive particles are incorporated in a base material consisting of a metallic alloy having special physical characteristics. Preferred compositions include one or more of a reducing agent, a control and embrittling agent, and an oxygen scavenging agent.

In accordance with the present invention, the surprising and unexpected discovery has been made that a compacted, metal-like abrasive article which contains diamond abrasive particles distributed in a novel alloy may be made at relatively low temperatures and relatively low compression forces to provide a product of high mechanical strength, relatively low porosity, in which the abrasive material is firmly and securely held, and which resists glazing, overheating, and inordinate wear in use.

It is an important feature of the abrasive compositions and articles of the invention that the diamond particles, together with other materials, including, in a preferred embodiment of the invention, a reducing agent in the form of a hydride, a control and embrittling agent in the form of a carbide, and an oxygen scavenging agent in the form of -a stearate are incorporated in a unique base material consisting of an iron-silicon alloy to provide a compacted and mechanically stable unitary physical structure of improved abrasive characteristics and grinding capabilities.

A related feature of the abrasive articles produced in accordance with the invention is that the diamond particles are held in a combination of physical securement coupled with chemical bonding.

An important feature of the invention is the use of an oxygen scavenger chemical agent as a means to limit undesirable and detrimental oxidation particularly at interfaces between the diamond abrasive particles and the other components of the composite article produced.

A related feature of the invention is the incorporation in the composite of an agent to control the hardness and the ductility as well as the brittleness of the final abrasive article produced.

Yet, another important feature of the invention is the incorporation in the abrasive composition of a material chemically reactive with other components thereof, in-

.cluding silicon and carbon (the diamonds) to form reaction products contributing to the overall strength and physical stability of the final composite.

An important feature of the invention is the use, in conjunction with diamond abrasive particles, of a base material or metallic alloy, a metallic hydride, and a ice control and embrittling agent and a material effective as an oxygen scavenger to obviate oxidation of the abrasive article produced and to enhance the interbonding of the constituents of the article.

An object of the invention is the incorporation, in combination with other components of a composite abrasive article, of an agent to control the abrasive resistance" of the resulting matrix, ensuring that the matrix will not erode too rapidly in use.

It is a feature of the invention that a metallic hydride is incorporated in the composite to minimize the formation of metallic oxides, to reduce, chemically, any metallic oxides present to pure metal, and thus to improve the physical and chemical bonding between diamonds and the metallic matrix.

It is an important feature of the invention that the composite aggregate is fabricated through the concurrent application of controlled heat and pressure to provide a unitary abrasive article having unique physical strength and abrasive characteristics.

Other and further features and advantages of the invention will become apparent from a consideration of the more detailed description which follows.

In order to disclose more clearly the nature of the present invention, specific examples are set forth below, it being understood, however, that the examples are intended neither to delineate the scope of the invention nor to limit the ambit of the appended claims.

The basic and essential components of the composition of the invention are a unique low-carbon alloy of iron and silicon and an abrasive material distributed therethrough. In the following examples the concentrations of components are indicated in parts by weight, except as may otherwise be indicated.

Example 1 The fundamental formulation of the invention, useful to produce abrasive articles of superior quality and lengthened useful life is the following:

A. Silicon-iron alloy 95.5 B. Abrasive powder 5.0

The abrasive powder is preferably diamond powder. Other abrasive materials such as silicon carbide, boron nitride, and aluminum oxide may be used. When diamonds are used, the concentration is preferably in the range of from about 5 to carats per cubic inch. The concentration of abrasive may cover a board range but is ordinarily from about /2% to 25% by weight. The siliconiron alloy is of a low carbon (ordinarily less than 0.1%) content and functions as the novel base material or binder meta An iron-silicon alloy containing about 9% of silicon is preferred, although compositions containing silicon in the range of from about 2 /2 to 22% have been found suitable. Within this range, concentrations of from 6 to 12% have been established as particularly useful.

Example 2 In a somewhat modified formulation there is incorporated into the composition of the invention an oxygen scavenging agent.

A. Silicon-iron alloy 95.5 B. Abrasive powder 5.0 C. Lithium stearate 1.5

The lithium stearate is believed to fulfill the role of an oxygen scavenging agent and to react at elevated temperatures to preclude and obviate the formation of oxidation products in the composite article of the invention. Although other chemical compounds such as calcium, barium, zinc and strontium stearate are believed to function in somewhat the same manner and to serve the same role, the results obtained when lithium stearate is used are superior.

A preferred concentration of lithium stearate in the composition of the invention is about 1 /2% by weight. Lesser concentrations in the range of 0.5% to 1% may be used, as well as concentrations up to 2% and higher. As presently indicated, a concentration of at least 0.1% by weight is essential in order to achieve the special benefits which the chemical compound provides.

Example 3 Another preferred formulation embodying the invention includes zirconium hydride.

A. Silicon-iron alloy 95.5 B. Abrasive powder 5.0 C. Lithium stearate 1.5 D. Zirconium hydride 1.5

The zirconium hydride is believed to function both as a reducing agent and as an agent to establish and to preserve a high state of chemical activity of the surface of the other ingredients and of the abrasive material, facilitating and promoting important inter-surface reactions believed to result in the formation of inter-action products, for example, carbides, as the diamonds react with others of the agents present.

Example 4 In still another preferred formulation of the invention there is included a control and embrittling agent or carburizing agent believed to increase the hardness and to control the abrasive resistance of the final composite article. Silicon carbide serves these functions.

A. Silicon-iron alloy 95.5 B. Abrasive powder 5.0 C. Lithium stearate 1.5 D. Zirconium hydride 1.5 E. Silicon carbide 1.5

Preferably, the physical size of the silicon carbide particles used is about three mesh sizes (US. Standard) below the size of the major abrasive (diamond powder), and the concentration is preferably in the range of from about 0.4-4.5% by weight although concentrations up to about by weight have been found suitable. Under special circumstances, the silicon carbide may be eliminated entirely. It is believed that during the manufacturing process at least some of the zirconium hydride is reduced to zirconium and that the aflinity of zirconium for silicon and for carbon results in the formation of both zirconium silicide and zirconium carbide, the reaction contributing toward the establishment of an integrally bonded composite article.

While the examples have been presented in a manner to emphasize the role each ingredient plays in the composition, it should be understood that the basic composition consists of the iron-silicon alloy and the abrasive. The other ingredients may be added to this basic composition singly or in any preferred grouping, depending on the intended use and the related demands upon the tool to be fabricated.

Utilizing any of the specific formulations of the foregoing examples, or any of the others of the many formulations disclosed and inherently embodied in the subject invention, a preferred manufacturing procedure for producing the abrasive articles of the invention is the following:

The silicon-iron alloy (with or without other bond materials, such as C, D, and E) was mixed and blended with the abrasive diamond powder. Any preferred blending technique may be used. The blend was then loaded into a graphite (carbon) mold of the desired shape and an initial cold press in the range of about 250 pounds per square inch was applied to set the material in the mold. The filled mold was then introduced into an oven and live pressure was applied and maintained throughout the heating cycle, the applied presure being in the range of 800 p.s.i. and the temperature being raised to about 1130 C. (2100 F.) over a time interval of about 20 minutes. The temperature was then held at the 1130 C. point for about an additional 25 minutes after which the mold and its contents were removed from the oven and allowed to cool. The product was then removed from the mold.

It will be appreciated that any preferred mold cavity, conforming to the desired final shape of the tool or article required, may be used. Preferably, the mold is of graphite since this material is inexpensive and has the additional advantage of maintaining a reducing atmosphere, thus to minimize any destructive oxidation which might normally occur during the heating process. If desired, ceramic molds may be used.

In one preferred embodiment of the ultimate article of the invention, there is produceda wheel-like tool which is shaped at its radially peripheral encircling margin to define a concave contour the counterpart of which is to be impressed and formed on the edge portion of a glass panel or the like. It will be appreciated that any other preferred tool or shaped or ground product may be fabricated in accordance with the teachings set forth above.

It has been found that tools and abrasive articles produced in accordance with the invention are of an improved hardness and are highly resistant to abrasion and corrosion. Additionally, the tools wear in such a manner as fully to take advantage of the abrasive particles which are exposed and, thereafter, undergo automatic resurfacing so that new diamond cutting edges are exposed for further functional use. It is an important feature of the tools made in accordance with the invention that the metal binder or matrix material is of a hardness consistent with the automatic sequential establishment of new abrading surfaces as the tool wears.

While the invention has been described in conjunction with a preferred embodiment and preferred procedures, it is evident that the invention is not limited thereto. For example, while diamonds are the preferred abrasive, other particles may be used for particular applications. Further modifications of the method and products disclosed herein which fall within the scope of the following claims will be immediately evident to those skilled in the art. To the extent that these changes and modifications are within the scope of the appended claims, they are to be considered a part of this invention.

What is claimed is: 1. A molded abrasive article of predetermined physical configuration and comprising an intimate mixture of physically blended, physically intercemented, substantially homogeneously distributed materials including, in combination:

an alloy of iron and silicon, constituting at least about by weight of said article, said alloy including silicon in a concentration of from about 2 /2% to about 22% by Weight; and

an abrasive diamond powder dispersed in said alloy,

said powder being present in said article in a concentration of from about /2% to 25% by weight.

2. The article as set forth in claim 1 and further comprising zirconium hydride present at a concentration of about 1.5% by weight.

3. The article as set forth in claim 2, wherein the alloy of iron and silicon and the zirconium hydride are present in the following concentrations in parts by weight:

Iron-silicon alloy 95.5 Zirconium hydride 1.5

4. The article as set forth in claim- 1 and further comprising silicon carbide present at a concentration of about 1.5% by weight.

5. The article as set forth in claim 1 and further comprising zirconium hydride present at a concentration of about 1.5% by weight and silicon carbide present at a concentration of about 1.5% by weight.

6. The article as set forth in claim 1 wherein said abrasive diamond powder is present at a concentration in the range of from about 5 to 140 carats per cubic inch.

7. The article as set forth in claim 5 wherein the alloy of iron and silicon, the zirconium hydride, and the silicon carbide are present in the following concentrations in parts by weight:

Iron-silicon alloy 95.5 Zirconium hydride 1.5 Silicon carbide 1.5

8. The article as set forth in claim 1 and further comprising lithium stearate present at a concentration of about 1.5% by weight.

9. The article as set forth in claim 8 wherein the alloy of iron and silicon and the lithium stearate are present in the following concentrations in parts by weight:

Iron-silicon alloy 95.5 Lithium stearate 1.5

carbide, and the lithium stearate are present in the following concentrations in parts by weight:

Iron-silicon alloy 95.5 Zirconium hydride 1.5 Silicon carbide 1.5 Lithium stearate 1.5

References Cited UNITED STATES PATENTS 3,239,321 3/ 1966 Blainey et al. 51309 2,529,722 '1 1/ 1950 Chester 51309 3,496,682 2/ 1970 Quaas et al 51309 3,316,073 4/ 1967 Kelso 51309 3,372,010 3/1968 Parsons 51--309 3,389,981 6/ 1968 Strauss 51309 3,574,580 4/1971 Stromberg et al 51309 3,596,649 8/ 1971 Olivieri 51309 DONALD J. AR NOLD, Primary Examiner US. Cl. X.R. 51304, 307 

